According to DIN 55946 (German Industrial Standard 55946) bitumens are a dark colored, semisolid to brittle, meltable, high molecular weight hydrocarbon mixtures which are obtained in the careful refining of petroleums and the portion of the natural asphalts as well as mineral wax and montan wax soluble in carbon disulfide (see Rompp Lexikon der Chemie, 7th Edition, page 377).
These kinds of materials which in the Anglo-Saxon region (above all the U.S.A.) are designated as asphalt are employed admixed with limestone powder, granite powder, basalt powder, greenstone powder and gabbro powder in the building of streets.
In this connection of especial significance is the use of natural asphalt.
Natural asphalt can be employed in admixture with bituminous binders according to DIN 1995 for the production of mortar rich coating layers (e.g., cast asphalt, asphalt concrete, sand asphalt and asphalt mastic). A natural asphalt of this type is, e.g., Trinidad-Epure (Trinidad-refined) which has the following composition:
______________________________________ Soluble bitumen 53 to 55 weight % Mineral portion 36 to 37 weight % Residual constituents 9 to 10 weight % ______________________________________
(compare Handbuch fur Strassenwesen Planung-Bau-Verkehr-Betrieb 1979, Otto Elsner Verlagsgesellschaft, Darmstadt).
Trinidad-Epure as well as the other known natural asphalts have the disadvantage that in spite of the very high filler content they are solid and must be melted before use.